Radio receiving system



F. A. KOLSTER RADIO RECEIVING SYSTEM w Sept. 4, w2s.,

Filed June 2, '1924;

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This invention relates toe for re ceiving signals transmitted by radio, T and more particularly to such a system arranged m the purpose of communicating with each other. Such an installation is commerclally feasible in many localities where the traific is sufficiently heavy. It is also evident that the reliability of the system of communica-f tion in maintaining favorable signaling coni iditions depends a great deal upon the degree" of selectivity that the receiving station has. which-determines. its freedom from lasing hamperedby interfering signals. stat cs or strays. It is one of the objects of my invem tion to increase'substantially the selectivity of such a receiving system. y In order to assist inthe accomplishment of this result, I use anoil' or loop antenna for 25 receiving the signalsf As is now well under v stood, such an absorbing CIICUIl, exhibits direcs tional receptive qualities for example, it will receive the greatest amount of energy when the plane of the coil is in line with the direc- 50 tion from which radiations emanate, and 1t will receive the least amount of energy when the plane of the coil is normal or at right" angles to this direction. .By the plane of the coil is meant that plane which is passed through the coil perpendicular to the axis of the winding, and substantially through the geometric center of the axial length of the coil. Between these two extreme positions the response has been found to have mterme' diate values, gradually varying from minimum to maximum as the plane of the coil with respect to direction of the source isvaried from normal position to coincident position. It is another object of my invention to alter this functional relation between.

the angular position of the coil plane, and

the degree of response, whereby the coill'is caused to respond to the radiations to a dimimshed extent than otherwise, except when the plane-is in the'maximum response posi jt on, which corresponds to the relative posit on of the coiland the source with which It 15 deslred to communicate. Due to this hy'controlling to some extent, the direction the wave front that radiates from an in ,tenfermq source, so that such .w'avez front strikes the coil plane more nearly in a normal on the receiving system. It is therefore an-- features. some" of whichwith the foregoing;

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name nnonzvma srsrm arrangement. interfering stations out of line with the coil plane will not affect the coil to as great an extent as heretofore. and the danger of obscuring the desired signal'by: such interference is very materially lessened. These advantageous results are produced direction. and therefore with areduced effect other object of my invention to control the dlrectlon of movement of-the wave front from an interfering! source, to mini i i terference; I My invention possesses other advantageous will set forth at len th in the following descmptlom'where I shall outline in full that form of the invention which I have selected for illustration in the drawings accomoany 'to 1139! and forming part of the present apnlica tron. Although I have shown in the draw mas but one embodiment of mvjinvention,

I do not desire to be limited fthereto, since. the invention as expressed in the claims may be embodied in other forms also, 1;

Referring to the drawings: I F gure l is a diagrammatic plan lview of a receiving system embodyingmy invention :3 an

I 1 Fig. 2 is a diagram illustratinzzthe onset of my invention to suppress interference.

;; In'Fig. 1, I show a coil 11 with its plane fixed in the direction that causes its response a maximum to a transmitting station 12; In order to perceive the signals, any desired form of radio receiver 13 may be connected to the coil. In addition, a variable condenser 14 is shown, connect-ed serially to coil 11, for tuning this circuit very sharply to the frequency of communication.

The point 15 represents one of any number of interfering sources, either transmitting stations, or focal points of strays or the like. It is well understood atthe present time that the response of the coil to such a source is of a less degree than to station 12, since the plane of the coil 11 is displacedby a substantial angle a from the direction of source 15. The degree of response may in fact be plotted for such an installation, as shown by-the figure 8 characteristic 16 of Fig. 2. In this figure, the response to radiation from station 12 may be represented by the line O17, and is a maximum; while the response to radiation from any other source such as 15 is represented by the line 0-18. These lines are drawn respectively in the directions of the corresponding sources, and when fully plotted for all directions, it will be found that the well-known figure 8 characteristic 16 is obtained.

A study of this characteristic reveals the fact that the response is a minimum in a direction perpendicular to the plane of coil 11, and rapidly increases as the direction approaches that of station 12. It is evident, therefore, that if it were possible to change the direction of the radiations before they reach coil 11 SO as o ring h m more n arly gated in the direction of its plane, and a conperpendicular to the plane of coil 11, the degree of res use would be reduced. For example, if t e radiations from point 15 were so changed in direction that apparently they proceed in a direction shown by the line 19, then the degree of response would be represented by the line O-20, which is much shorter than the line O18. Plotting this new degree of res onse alon line O18, it will be represente by line -21. My aim is to shift the apparent direction of all possible sources outside of the line 22 nearer the perpendicular position, so that the resultant characteristic is materially flattened, as illustrated by the heavy curve 23. In this way, the directional characteristic approaches more nearly the ideal straight line form, which would correspond to no res onse whatever of the coil to a station fa ling 01f of line 22.

I accomplish this desired result by providing a wave front distorter or guide, that leads the radiations more nearly perpendicularly toward the coil plane for stations falling off the line 12. This guide for the radiations takes the form of a long conductor 24, Fig. 1,

that is placed at right angles to the plane of coil 11. This conductor should preferably extend equally on both sides of the coil, and be provided with some form of tuning device, such as the variable inductance 25. For radiations proceeding from the station 12, this conductor has no. appreciable eflect, since "'"it is symmetrical with respect to the wave front, and cannot therefore change its direction. But for radiations proceeding from other points, such as from source 15, the conductor 24 serves to deflect the wave front a Since the arrangement has no effect on the radiations proceeding from source 12, this conductor could be tuned to an interfering frequency which is close, or even equal to that associated with source 12. Although the wire 24 is laced near the coil 11, and carries current ue to energy absorbed from the interfering stations, such current has no harmful effect on the reception, due to the fact that the wire 24 is fixed in non-inductive relation to the coil 11. It is evident that the provision of such an arrangement to alter the wave front of interfering radiations has a marked effect in reducing interferencewhile maintaining thedegree of response to the desired radiations unimpaired.

I claim: r 1. In a system for receiving electromagnetic radiations, a coil arranged to be responsive to a maximum degree to radiationsv propanetic radiations, a coil arranged to be responsive to a maximum degree to radiations propagated in the direction of its plane, a

conductor arranged adjacent the coil and extending substantially at right angles to its plane, said conductor being open ended and relatively long as compared to the coil and means for tuning said conductor.

3. In a system for receiving electromagnetic radiations, an absorbing circuit havin nonuniform directional characteristics, an capable of movement to be affected most strongly by radiations from a desired direction, and means for altering the direction of the wave front of radiations from substantially all other directions, comprising a conductor arranged adjacent the circuit and at right angles to the desired direction, said conductor being open ended and relatively long as compared to the absorbing circuit.

'4. In a system for receiving electromagnetic radiations, a loop antenna having directional characteristics, means for selectively tuning said antenna, a detector circuit electrically associated with said antenna, and means for altering the wave front of radio energy which is received from a direction other than perpendicular to the axis of said loop, said means comprising an elongated conductor relatively greater in length then the diameter of said loop and arranged at an angle to the plane of said loop.

p 5. A radio antenna comprising a closed the diameter of said loop and arranged at an loop having'flirectional characteristics, means angle to the plane of the loop, and means infor selectively tuning said loop, a signalling sorted in said conductor for tuning the same. 10 circuit coupled to sand loop, and means for In testimony whereof, I have hereunto Set 3 aoentuating the directional characteristics of my hand.

the loop comprising a substantially linear open ended conductor of greater length than FREDERICK A. KOLSTER. 

